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Consider the figure and answer the following questions.
(i) Cell ' $A$ ' has $E_{\text {cell }}=2 \mathrm{~V}$ and Cell ' $B$ ' has $E_{\text {cell }}=1.1 \mathrm{~V}$ which of the two cells ' $A$ ' or ' $B$ ' will act as an electrolytic cell. Which electrode reactions will occur in this cell?
(ii) If cell 'A' has $E_{\text {cell }}=0.5 \mathrm{~V}$ and cell 'B' has $E_{\text {cell }}=1.1 \mathrm{~V}$ then what will be the reactions at anode and cathode?
(i) Cell ' $A$ ' has $E_{\text {cell }}=2 \mathrm{~V}$ and Cell ' $B$ ' has $E_{\text {cell }}=1.1 \mathrm{~V}$ which of the two cells ' $A$ ' or ' $B$ ' will act as an electrolytic cell. Which electrode reactions will occur in this cell?
(ii) If cell 'A' has $E_{\text {cell }}=0.5 \mathrm{~V}$ and cell 'B' has $E_{\text {cell }}=1.1 \mathrm{~V}$ then what will be the reactions at anode and cathode?
Solution:
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Verified Answer
(i) Cell with lesser value of emf will act as electrolytic cell. Therefore ' $B$ ' with lesser value of emf will act as electrolytic cell.
The electrode reactions will be
At cathode : $\mathrm{Zn}^{2+}+2 e^{-} \longrightarrow \mathrm{Zn}$
At anode3: $\mathrm{Cu} \longrightarrow \mathrm{Cu}^{2+}+2 e^{-}$
(ii) If cell ' $B$ ' has higher emf then it will act as galvanic cell. Now it will push electrons into cell ' $A$ '.
In this case the reactions will be
$$
\begin{aligned}
&\mathrm{Zn} \longrightarrow \mathrm{Zn}^{2+}+2 e^{-} \text {(At anode) } \\
&\mathrm{Cu}^{2+}+2 e^{-} \longrightarrow \mathrm{Cu} \text { (At cathode) }
\end{aligned}
$$
The electrode reactions will be
At cathode : $\mathrm{Zn}^{2+}+2 e^{-} \longrightarrow \mathrm{Zn}$
At anode3: $\mathrm{Cu} \longrightarrow \mathrm{Cu}^{2+}+2 e^{-}$
(ii) If cell ' $B$ ' has higher emf then it will act as galvanic cell. Now it will push electrons into cell ' $A$ '.
In this case the reactions will be
$$
\begin{aligned}
&\mathrm{Zn} \longrightarrow \mathrm{Zn}^{2+}+2 e^{-} \text {(At anode) } \\
&\mathrm{Cu}^{2+}+2 e^{-} \longrightarrow \mathrm{Cu} \text { (At cathode) }
\end{aligned}
$$
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